Chemical analysis by time dispersive ion spectrometry

Abstract

Methods and apparatus for time dispersive ion spectroscopy such as ion mobility spectroscopy. The methods include ionizing molecules of a sample and controllably admitting pulses of the resulting ions into a drift region. The drift region has an electric field therein which forces the admitted ions through the drift region. Ions emitted from the drift region during a gate open period simultaneous with the ion admission period are exclusively detected resulting in an ion detection signal. Data is recorded for the frequency rate at which the ion pulses are admitted to the drift region and the associated ion detector signal. The frequency of admitted ion pulses is scanned over a relevant range during which the ion admission period also varies. Data recorded for frequency and ion detection can be recorded and/or transformed such as by a Fourier transform to produce time dispersive spectra in the form of ion intensity or quantity as a function of the time period necessary for the ions to transit the drift region. Such spectra are useful in identifying constituents such as organic compounds contained in the sample. The methods and apparatus allow rapid analysis of samples and can be used to simultaneously analyze discharges from sample separation apparatus such as a capillary gas chromatograph.